In order to make aircraft passengers comfortable, and in order to transport them between an airport terminal building and an aircraft in such a way that they are protected from the weather and from other environmental influences, passenger loading bridges are used which can be telescopically extended and the height of which is adjustable. For instance, an apron drive bridge in present day use has a plurality of adjustable modules, including: a rotunda, a telescopic tunnel, a bubble section, a cab, and elevating columns with wheel carriage. Of course, other types of bridges are known in the art, such as for example nose loaders and pedestal bridges.
Unfortunately, the procedure for aligning the passenger loading bridge with a doorway of the aircraft is a time consuming operation. First, the pilot taxis the aircraft along a lead-in line to a final parking position within the gate area. Typically, the lead-in line is a physical marker painted onto the tarmac, and it is used for guiding the aircraft along a predetermined path to a final parking position. Additional markings in the form of stop lines, one for each type of aircraft, are provided at predetermined positions along the lead-in line. Thus, when the nose gear of a particular type of aircraft stops precisely at the stop line for that type of aircraft, then the aircraft is at its final parking position. Of course, the pilot's view of the tarmac surface from the cockpit of an aircraft is limited. This is particularly true for larger aircraft, such as a Boeing 747. Typically, therefore, the pilot relies upon instructions provided by one of a human ground marshal together with up to two “wing walkers”, and an automated docking guidance system to follow the lead-in line. Alternatively, stop bars are located on a pole that is fixedly mounted to the ground surface, including appropriate stop bars for each type of aircraft using the gate. Further alternatively, a tractor or tug is used to tow the aircraft along the lead-in line to its final parking position.
Secondly, the passenger loading bridge is aligned with the parked aircraft, which in the case of an apron drive bridge may involve extending the bridge by 10 to 20 meters or more. Driving the bridge over a long distance is very time consuming because often the rate at which the bridge is moved is limited in order to reduce the risk of colliding with ground service vehicles or personnel, and to avoid causing serious damage to the aircraft in the event of a collision therewith. Manual, semi-automated and fully-automated bridge alignment systems are known for adjusting the position of the passenger loading bridge relative to the parked aircraft.
Manual bridge alignment systems typically are preferred by the airlines because a trained bridge-operator is present and is able to observe directly the movements of the bridge relative to the parked aircraft. The bridge-operator uses a control panel located within the cab section to adjust the bridge each time an aircraft arrives. Accordingly, the probability that the bridge will collide with a parked aircraft during an alignment operation is relatively small. Unfortunately, the time that is required to align the passenger loading bridge with the parked aircraft is greatest with a manual alignment system, which translates directly into longer turnaround times for the airlines and increased passenger inconvenience. Additional delays may also occur from time to time with a manual bridge alignment system, for instance in the event that the aircraft stops at its final parking position before the bridge-operator arrives. It is a disadvantage of the manual bridge alignment systems that bridge-operators must be employed and trained to operate the system, which increases operating costs. It is a further disadvantage of the manual bridge alignment systems that operator experience and/or caution may further limit the speed at which the passenger loading bridge is actually moved.
Semi-automated bridge alignment systems are also known, whereby the bridge is moved rapidly to a preset position under the control of a computer. WO 96/08411, filed Sep. 14, 1995 in the name of Anderberg, describes a semi-automated system for controlling the movement of a passenger loading bridge. When an aircraft has landed, a central computer transmits information on the type of aircraft to a local computer of the passenger loading bridge at an assigned gate. The local computer accesses a database and retrieves information on the positions of the doors for the type of aircraft that has landed, as well as information on the expected final parking position for the type of aircraft at the assigned gate. The local computer uses the retrieved information to determine an absolute position of the door with which the bridge is to be aligned. Accordingly, the passenger loading bridge is moved under computer control to a position close to the determined position of the door, for example within 2–10 meters. Optionally, the bridge is preset to this position before the aircraft has stopped moving.
WO 01/34467, filed Nov. 8, 2000 also in the name of Anderberg, teaches that the above system is reliable only for movement to a position close to the parked aircraft. Thus, the bridge has to be operated manually during the remaining 2–10 meters of its movement. The WO 01/34467 reference also teaches an improvement to the above system, in which electromagnetic sensors are disposed along the outboard end of the passenger loading bridge for transmitting a set of electromagnetic pulses in different directions and for detecting electromagnetic pulses after reflection from an aircraft. Based on the elapsed time between transmitting and detecting the electromagnetic pulses in different directions, a profile of distance as a function of direction is obtained. From the measured distance versus direction profile and the information stored in the computer, it is then possible to maneuver the bridge the rest of the way from the preset position to the door of the parked aircraft. Unfortunately, when the aircraft fails to stop at the expected final parking position, the preset position will be misaligned with the actual position of the aircraft door, and human intervention will be required in order to complete the alignment operation.
Other automated systems have been proposed, for instance an automatic loading bridge which uses video cameras in the control of the bridge as described by Schoenberger et al. in U.S. Pat. No. 5,226,204. The system uses the video cameras to capture images of an aircraft to which the bridge is to be aligned, which images are provided to a computer for image processing. An object of the image processing is to locate doors along the lateral surface of the aircraft facing the passenger loading bridge. The bridge is then moved automatically in a direction toward a predetermined door of the parked aircraft. Unfortunately, the system described in U.S. Pat. No. 5,226,204 suffers from several disadvantages. For instance, a very sophisticated image processing system is required to locate a door along the side of an aircraft from a distance of up to 15 meters or more. Factors such the weather, ambient lighting conditions and the presence of intervening ground support vehicles may also become very significant over such a large distance. Furthermore, the bridge still is required to move a significant distance during the alignment operation, which requires a finite amount of time and poses a hazard to ground service vehicles and personnel.
Thus, it has been a continuing problem to provide a bridge alignment system which is capable of safely and reliably aligning a passenger loading bridge with an aircraft. In addition, there has been a long-standing, unfulfilled need for a bridge alignment system which reduces the amount of time that is required to complete each bridge alignment operation.
In view of the limitations of the prior art alignment systems discussed above, it is an object of the instant invention to provide an alignment system for aligning a door of an aircraft to a passenger loading bridge.
It is another object of the instant invention to provide an alignment system which reduces the amount of time that is required to complete each bridge alignment operation.